1. Field of the Invention
This invention relates to an image pickup apparatus and an image correction method allowing appropriate black balance correction in image pickup in a dark environment.
2. Description of the Related Art
Conventionally, an image pickup apparatus that is capable of sequentially converting optical images formed by an image pickup optical system into image signals by a photoelectric conversion device or the like and of storing the image signals thus obtained in a storage medium as pieces of image data of a predetermined format, and configured by including an image display device, for example, a liquid crystal display (LCD), that reproduces/displays the image data stored in the storage medium as an image, such as a digital camera or a camcorder (hereinafter referred to collectively as camera(s)), has been put to practical use and widely used.
When using this type of camera and performing image pickup of a night scene by a long exposure, for example, if the exposure time is long, artificial light from street lamps, neon lights or the like may affect the entire screen. For example, a region in the screen which is supposed to be dark, such as a region of night sky, may not be black, and may be shown to be brighter than it looked due to the influence of artificial light or the like, or faint light images of stars or the like may be erased. Also, the original color of a target object in a dark place may not be reproduced due not only to the artificial light, but also to unintentional diffraction of environmental light.
Accordingly, various proposals are conventionally made in, for example, Japanese Patent Application Laid-Open Publication No. 2005-45558, with respect to an image correction processing technique for acquiring an image that is closer to the way of being seen by human beings by taking into account the influence of harmful light such as artificial light.
An image pickup apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2005-45558 mentioned above performs black balance control of correction in a neutral axis direction, also in the case the darkest point in the image is shifted from a neutral axis, by taking into account the adaptation effect of human eyes to black (the rate of dark adaptation).